1. Field of the Invention
The present invention relates to the preparation of a new class of polymers, namely methacrylated urethane/urea copolymers containing moisture curable silicone soft segments in the polymer backbone, and compositions prepared therefrom. More specifically, this invention relates to the preparation of a copolymer derived from a partially methacrylated urethane prepolymer and an amino alkylene dialkoxysilanol terminated silicone prepolymer. These materials therefore have olefinic functionality and alkoxysilane functionality, allowing for cure by means of free radical (photo or anaerobic) mechanisms, as well as by moisture cure.
2. Description of Related Technology
It is known that diisocyanate end-capped urethane, containing both hard block and soft block segments can be prepared by proper control of the stoichiometry and steps in the process. For example, a diisocyanate end-capped hard block segment can be prepared from a diisocyanate and a rigid diol as a first stage or step, followed by a reaction of this diisocyanate end-capped prepolymer with a long chain diol to yield a diisocyanate end-capped polyurethane with soft and hard segments.
U.S. Pat. No. 4,684,538 to Klemarczyk discloses a method to produce acrylate end-capped polysiloxane urethane compositions in which siloxane-carbinol bonds are in the repeat unit of the polymer chain and which are capable of fast UV cure.
U.S. Pat. No. 5,760,155 to Mowrer describes a novel polysiloxane urethane composition in which one of the repeat units in the polymer back bone is comprised of urethane Si bonds, i.e. 
The disadvantage of this kind of repeat unit is the inherent hydrolytic instability.
The interest in polysiloxane/polyurethane compositions is further exemplified by U.S. Pat. No. 4,839,443 to Akutus et al., whereby improved surfaces characteristics are alleged. Linear silicone-urethane copolymers are described as providing films of high strength and elasticity when cast from aqueous dispersions.
There is a definite need for a new process which provides polyurethane siloxane copolymers having excellent toughness and adhesive properties. It would be even more advantageous to produce an acrylated end-capped urethane-urea siloxane copolymers without the limitations of prior compositions.
One aspect of the present invention relates to a new class of (meth)acrylated urethane/urea copolymer compositions having moisture curable silicone segments and photocurable acrylated end-caps. The compositions are particularly useful in a variety of applications such as in the adhesive, coating, caulking and potting areas. These compositions have found to be particularly useful in the electronic, automotive, industrial and consumer fields.
In the synthesis of acrylate end-capped polysiloxane/urethane urea copolymers of the present invention, a process in forming polysiloxane/urethane-urea units was developed to minimize the concentration of available isocynate groups which cause biuret formation. This process, whereby the acrylated polyurethane prepolymer is formed first, and the polysiloxane units are incorporated in a second step, allows for the formation of a dual cured end-capped aminoalkylene dialkoxy silicone/polyurethane material having minimum biuret formation. Moreover, since the polymer is acrylated in the first step of the process it is free of hydroxyalkyl (meth)acrylate, thereby alleviating environmental issues relating to by-products.
In one aspect of the invention there is provided a curable polymer having the structure I: 
wherein A and B may be the same or different and have the structure: 
(i) wherein Q is 
xe2x80x83or 
xe2x80x83a is 2 to 3; R1 and R10 may be the same or different and may be a substituted or unsubstituted C1-C10 alkylene group; R is H or CH3; and
(ii) wherein R4, R6, R7, R8, R9 and R11 may be the same or different and are substituted or unsubstituted hydrocarbon radicals; R11 may also be saturated or unsaturated, for example, it may contain a vinyl group or a (meth)acrylate group; R2, R3 and R5 may be the same or different and are divalent substituted C1-C40 aliphatic, cycloaliphatic or aromatic hydrocarbon radicals, or a polyol, polyester, or polyalkylidene having a weight average molecular weight from about 200 to about 5,000; n is an integer from 1-1000, desirably 1-10 and more desirably 1-5; p is an integer from 1-1200, desirably 1-200 and more desirably 1-100.
In a further aspect of the invention there is provided a curable polymer which includes the reaction product of:
a) a reactive prepolymer component having a radiation-curable group proximal to one terminus of the prepolymer and an isocyanate group proximal to the other terminus of the prepolymer; and
b) an aminoalkylenedialkoxysilyl-terminated polydiorganosiloxane.
In a still further aspect of the invention there is provided a dual curing composition which includes
a) a (meth)acrylated urethane/urea silicone copolymer which includes the structure: 
xe2x80x83wherein A and B may be the same or different and have the structure: 
wherein R is H or CH3; R1 is a divalent substituted or unsubstituted C1-C40 aliphatic, cycloaliphatic or aromatic hydrocarbon radical; R2=R1 and may be the same or different; R3 is a polyol, polyether, polyalkylidiene, or polyester having a weight average molecular weight from about 200 to about 5,000; n is an integer from 1-1000; p is an integer from 1-1,200; R4 is a monovalent substituted or unsubstituted aliphatic, cycloaliphatic or aromatic hydrocarbon radical C1-C40; R5 is a substituted or unsubstituted divalent C1-C40 aliphatic, cycloaliphatic or aromatic hydrocarbon radical; R6=R4 and may be the same or different; R7=R6 and may be the same or different; and
b) a cure system for said copolymer.
In still a further aspect of the invention there is provided a method of preparing a curable (meth)acrylated polyurethane/urea silicone co-polymer which includes the step of:
reacting an isocyanate prepolymer having a terminal (meth)acrylate group with an noalkylenedialkoxysilyl-terminated polydiorganosiloxane.
In discovering the present invention, it has also been determined that the formation of biuret groups within the backbone structure is also less desirable because it leads to a more rigid structure due to increased crosslinking within the polymer system. The biuret crosslinking reaction occurs when an isocyanate group reacts with intermediate urea groups as shown in the reaction below. The formation of a biuret is schematically shown below: 
In contrast to conventional processes for forming polyurethane/acrylates which contain urethane linkages joining the hard and soft segments, the present invention uses a urea linkage to form these segments. This linkage is formed by the reaction of an isocyanate prepolymer with an aminoalkylene dialkoxy-terminated polydimethylsiloxane. The use of secondary amines as opposed to primary amines in this reaction is desirable because it minimizes the formation of biuret by-product. This is because the urea functionality unit formed in the isocyanate/amine reaction is capable of further reaction with available isocyanate group to form a crosslinked biuret structure. This increases the viscosity of the copolymer and limits the processability of the copolymer for further applications such as for adhesives, coatings and sealants. Thus, the present invention provides a process and composition which avoids the formation of biruets.
More particularly, the (meth)acrylated urethane/urea alkylaminoalkenedialkoxy siloxanes of the present invention include those represented by structure I: 
wherein A and B may be the same or different and have the structure: 
wherein Q is 
xe2x80x83or 
xe2x80x83a is 2-3; R1 and R10 may be the same or different and may be a substituted or unsubstituted C1-C10 alkylene group; R is H or CH3; R4, R6, R7, R8, R9 and R11 may be the same or different and are substituted or unsubstituted hydrocarbon radicals; R11 may also be saturated or unsaturated, for example, it may be a vinyl or (meth)acrylate group; R2, R3 and R5 may be the same or different and are divalent substituted C1-C40 aliphatic, cycloaliphatic or aromatic hydrocarbon radicals, or a polyol, polyester, or polyalkylidene having a weight average molecular weight from about 200 to about 5,000; n is an integer from 1-1,000, desirably 1-10 and more desirably 1-5; p is an integer from 1-1200, desirably 1-200 and more desirable 1-100.
Particularly desirable embodiments have the aforementioned structure I include those where A and B are identical and, for example, have the methacryloxy structure 
wherein R is methyl, R1 is ethylene, and Q is 
as shown in structure II: 
Another desirable aspect of the invention includes compounds where A and B have the methacrylamide structure 
wherein R and R1 are defined as above, R8 is methyl, and Q is 
Such a case corresponds to structure III: 
In still a further desirable embodiment, substituents A and B may be a substituted alkoxy silyl radical 
where a=2, R9 is methyl, R11 is methacryloxypropyl, R10 is propylene and Q is 
Such a case corresponds to structure IV: 
wherein 
R2 and R3 may be the same or different and are divalent cycloaliphatic or aromatic hydrocarbon radicals or are polyols, polyesters, or polyalkylidenes having weight average molecular weight from about 200 to about 5,000, most desirably 200-500; R2 is a hard segment such as an isophorone diradial; R3 is defined as also a hard segment, such as a propocylated bisphenol A diradial; n is an integer 1-1000, desirably 1 to 10, and more desirably 1-5; p is an integer 1-1,200, desirably 1-200 and most desirably 1-100.
The compositions of the present invention are curable by multiple mechanisms. For example, compositions containing the inventive polymers may be subjected to UV light in the presence of a photo initiator to cure or gel the material, and/or be allowed to cure by moisture under ambient conditions. Either or both of these mechanisms may be used to cure the compositions. In one desirable embodiment, as represented in structure II above, a methacrylated urethane/urea copolymer containing moisture curable silicone soft segments and urethane/urea hard segments is provided.
Polymer Synthesis
The polymers of the present invention are formed via a multiple step or staged process.
Preparation of Isocyanate-terminated Urethane Hard Segments (A-Stage Prepolymer)
An A-stage prepolymer may be prepared from a variety of diisocyanate monomers and diols, thereby producing an isocyanate end-capped prepolymer composition of various molecular weights, with soft and/or hard block segments, as determined by the reactants as shown in Equation V, below, to give the A-staged prepolymer V. Desirably, the final curable polymers of the present invention include both hard and soft segments, although the soft segment is desirably from the silicone portion to be discussed further herein. 
wherein R2 and R3 may be the same or different and is a divalent substituted aliphatic, cycloaliphatic or aromatic hydrocarbon radical, or polyol, polyester or polyalkylidene have an average molecular weight from about 200 to 5000, preferably 1000, and n is an integer from 1-100, desirably 1-100.
Examples of diisocyanates useful to produce the A-staged prepolymer V in Equation V above, can include, among others, isophoronediisocyanate (IPDI) tetramethylxylyldiisocyanate, (MXDI) toluene diisocyanate methylene diphenyl diisocyanate (MDDI) 1,6-hexane diisocyanate (HDI) or a substituted or unsubstituted aliphatic, cycloaliphatic or aromatic diisocyanate. Most desirable is isophorone diisocyanate (IPDI). In the A-stage process, other diisocyanates, such as tetramethyl xylylene diisocyanate (TMXDI) and toluene diisocyanate (TDI) and diols such as propolylated hydrogenated bis-phenol-A [HBPA(PO)2], and reactive diluents such as isobomyl methacrylate (IBOMA), hexane diol dimethacrylate (HDDMA), lauryl acrylate, and N,N-dimethyacrylamide (DMA), are useful. In preferred embodiments hydroxyethyl acrylate (HEA), hydroxyl propylacrylate (HPA), and hydroxypropyl(meth)acrylate (HPMA) are also useful. Additional non-limiting, representative examples of useful diisocyanates also include phenyl diisocyanate, 4,4xe2x80x2-diphenyl diisocyanate, 4,4xe2x80x2-diphenylene methane diisocyanate, dianisidine diisocyanate, 1,5-naphthalene diisocyanate, 4,4xe2x80x2-diphenyl ether diisocyanate, p-phenylene diisocyanate, 4,4xe2x80x2-dicyclo-hexylmethane diisocyanate, 1,3-bis-(isocyanatomethyl) cyclohexane, cyclohexylene diisocyanate, tetrachlorophenylene diisocyanate, 2,6-diethyl-pphenylenediisocyanate, and 3,5-diethyl-4,4xe2x80x2-diisocyanatodiphenyl-methane.
Numerous diols and polyols can be used to form the A-staged prepolymer, such as propoxylated hydrogenated bisphenol-A (HBPA (PO)2], ethoxylated hydrogenated 
bisphenol A (HEO2O), 4,8-bis(hydroxymethyl)tri-cyclo[5.2.1.02,6]decane (HMTD), 
or divalent substituted C1-C20 aliphatic cycloaliphatic or aromatic hydrocarbon radicals, or a polyol, such as polyether diol, polyester diol or polyalkylidiene diol having a weight average molecular weight from about 200 to about 5000. By selecting appropriate diols, polyurethane prepolymer can be produced containing both hard and soft segments, for example where HBPA(PO)2 or HMID are used to produce hard urethane segments and polyether diols are used to produce soft urethane segments. More desirably in the novel urethane A-staged prepolymer in Equation V above, the hard segment is formed from HMTD diol and a silicone soft segment introduced in a later step as described below. Additional non-limiting, representative examples of useful polyols also include 2,2-(4,4xe2x80x2-dihydroxydiphenyl)-butane; 3,3-(4,4xe2x80x2-dihydroxydiphenyl)-pentane; xcex1,xcex1xe2x80x2-(4,4xe2x80x2-dihydroxydiphenyl)-p-diisopropylbenzene; 1,3-cyclohexane diol; 1,4-cyclohexane diol; 1,4-cyclohexanedimethanol; bicyclic and tricyclic diols such as 4,8-bis-(hydroxymethyl)-tricyclo[5.2.1.02.6]decane; 2,2,4,4-tetramethyl-1,3-cyclobutanediols, hydroquinones, resorcinol, and 2,2(4,4xe2x80x2-dihydroxydiphenyl)sulfone, among others, as well as halogenated derivatives of the above, such as tetrabrominated ethoxylated bisphenol-A. These ring compounds may also be substituted with either reactive groups or unreactive groups such as alkyl groups containing about 1 to 4 carbon atoms.
Preparation of the Partially (Meth)acrylate End-capped B-Stage Prepolymer
The next step in the inventive process of preparing the curable polymers of the present invention involves partially capping the A-stage prepolymer with an acrylate to form a B-stage prepolymer VI. For example, A-stage polyurethane prepolymer in Equation VI, was partially capped with a hydroxyalkylacrylate 
as shown in Equation VI. 
where R is H or methyl, and R1 is a substituted or unsubstituted C1-C20 alkylene group, desirably ethylene.
It should be recognized that, notwithstanding the fact that the stoichiometry and the selected reaction conditions chosen yield the B-stage prepolymer as shown, a statistical distribution of reaction product mixture is expected. That is, a minor amount of polymer containing both acrylate ends may be produced, as well as a minor amount of A-stage prepolymer which may remain unreacted.
Preparation of the (Meth)acrylate End-capped Polyurethane/Urea Copolymer (C-Stage)
To begin with, a soft silicone block for use in the C-stage of the present invention is prepared. Nonlimiting examples of useful silicone soft blocks for use as a reactant in the C-stage of the present invention are shown in the reactions in Equation XI below. In this reaction, an amine terminated dialkoxy polydimethylsiloxane (PDMS) is prepared by end-capping a dihydroxy PDMS (silanol) with an amine functional trialkoxysilane. As the skilled artisan would recognize, the molecular of the silanol fluid may vary widely. A particularly useful molecular weight range includes mw about 4,000 to about 12,000, but molecular weights outside these ranges are useful. In the examples below, 4 EAM and 12 EAM are acronyms for bis[(ethylaminopropyl)dimethoxy silyl]polydimethyl siloxane of 4000 and 12000 molecular weights, respectively. 
Below is a non-limiting list of other useful variables for the soft silicone segment of the present invention:
In particularly desirable embodiments, R4 is ethyl, methyl or butyl, and R6 are methyl and R7.
The soft amine terminated segment silicone is then used in the aforementioned B-stage to produce the novel acrylated polyurethane/urea silicone block copolymer, which is capable of dual curing.
Preparation of Soft Silicone Block for Use in the C-Stage of the Present Invention
The last step (C-stage) in the synthesis of the novel (meth)acrylate end-capped polyurethane/urea copolymer containing dialkoxysilyl silicone soft segments is described by Equation VII. 
The B-stage preparation of the partially (meth)acrylated polyurethane hard block prepolymer described in Equation VI above represents a departure from conventional synthesis of acrylated polyurethane material containing hard and soft segment urethane blocks.
For example, conventional acrylated polyurethane process steps have included the formation of urethane hard and soft segments as depicted below in Equations VIII-X. 
In the above conventional process, Ar and Ar1 are aromatic groups, but it is also known to use aliphatic groups as well.
As shown below in conventional processes, the acrylate capping occurs in the final stage (C-stage), where in the present invention, such capping occurs in the intermediate stage (B-stage). 
Among the advantages of (meth)acrylate end-capping in B-stage as opposed to prior methods which acrylated in the C-stage, are: (1) complete consumption of the volatile acrylate end-capper occurs in the B stage, thereby eliminating undesirable trace amounts of this material in the final product, which can be an environmental concern; (2) a reduction in the concentration of isocyanate groups early on in the process (B-stage), i.e., the isocyanate/amine ratio is reduced, thereby minimizing the ability of secondary reactions to form biuret structures which cause a significant viscosity increase in the final product; (3) the use of secondary amines instead of primary amines reduces the amount of biuret formation. Thus, the inventive compositions are better able to form low viscosity resins which are desirable for final cure by one or more of mechanisms, i.e., photolytic, anaerobic and/or moisture cure.
Additives
A number of photoinitiators may be employed herein to provide the benefits and advantages of the present invention to which reference is made above. Photoinitiators enhance the rapidity of the curing process when the photocurable compositions as a whole are exposed to electromagnetic radiation. Certain metallocenes, such as xe2x80x9cIRGACURExe2x80x9d 784DC, may serve a dual purpose as both metallocene and photoinitiator.
Non-limiting examples of U.V. photoinitiators that are useful in the inventive compositions include benzoins, benzophenone, dialkoxy-benzophenones, Michler""s ketone (4,4xe2x80x2-bis(dimethylamino)benzophenone) and diethoxyacetophenone.
Examples of suitable photoinitiators for use herein include, but are not limited to, photoinitiators available commercially from Ciba Specialty Chemicals, under the xe2x80x9cIRGACURExe2x80x9d and xe2x80x9cDAROCURxe2x80x9d trade names, specifically xe2x80x9cIRGACURExe2x80x9d 184 (1-hydroxycyclohexyl phenyl ketone), 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholino propan-1-one), 369 (2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone), 500 (the combination of 1-hydroxy cyclohexyl phenyl ketone and benzophenone), 651 (2,2-dimethoxy-2-phenyl acetophenone), 1700 (the combination of bis(2,6-dimethoxybenzoyl-2,4,4-trimethyl pentyl)phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one), and 819 [bis(2,4,6-trimethyl benzoyl)phenyl phosphine oxide] and xe2x80x9cDAROCURxe2x80x9d 1173 (2-hydroxy-2-methyl-1-phenyl-1-propan-1-one) and 4265 (the combination of 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one); and the visible light [blue] photoinitiators, dl-camphorquinone and xe2x80x9cIRGACURExe2x80x9d 784DC. Of course, combinations of these materials may also be employed herein.
Other photoimtiators useful herein include alkyl pyruvates, such as methyl, ethyl, propyl, and butyl pyruvates, and aryl pyruvates, such as phenyl, benzyl, and appropriately substituted derivatives thereof. Photoinitiators particularly well-suited for use herein include ultraviolet photoinitiators, such as 2,2-dimethoxy-2-phenyl acetophenone (e.g., xe2x80x9cIRGACURExe2x80x9d 651), and 2-hydroxy-2-methyl-1-phenyl-1-propane (e.g., xe2x80x9cDAROCURxe2x80x9d 1173), bis(2,4,6-trimethyl benzoyl) phenyl phosphine oxide (e.g., xe2x80x9cIRGACURE 819), and the ultraviolet/visible photoinitiator combination of bis(2,6-dimethoxybenzoyl-2,4,4-trimethylpentyl) phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one (e.g., xe2x80x9cIRGACURExe2x80x9d 1700), as well as the visible photoinitiator bis (xcex75-2,4-cyclopentadien-1-yl)-bis[2,6difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium (e.g., xe2x80x9cIRGACURExe2x80x9d 784DC).
Non-limiting examples of moisture curing catalysts useful in the inventive compositions include a metal compound such as titanium, tin or zirconium. The moisture catalysts are employed in a curingly effective amount, which generally is from about 0.5 to about 5% by weight and desirably about 0.05% to about 2.5% by weight. Tetraisopropoxy titanate or tetrabutoxy titanate are particularly desirable. U.S. Pat. No. 4,111,890 list numerous others that are useful.
A variety of additional useful components may be added to the present inventive compositions. For example, reactive and non-reactive diluents may be added. Such diluents include, without limitation, isofomyl(meth)acrylate, dimethylacrylamide, (meth)acrylic acid and vinyltrimethoxysilane. Other useful additives include plasticizers, fillers, viscosity modifiers, pigments, stabilizers, and the like.